LabVIEW is a graphical programming system consisting of one or more "virtual instruments", each consisting of an input-output control panel, a dataflow block diagramming mechanism, and an associated icon. The block diagram specifies the connection, and hence the execution sequence (by means of dataflow rules) of an arbitrary set of built-in functions ("primitive icons") and user-specified functions ("virtual instruments"), thereby creating a hierarchical system of these virtual instruments. Refer to U.S. Pat. No. 4,901,221.
A number of significant improvements have been made which enable such a system to execute faster, use less memory, and more flexibly and compactly specify complex procedures.